This description relates to nanoparticle ion detection.
Mass spectrometers can be used to determine the identities and quantities of components that make up a solid, gas, or liquid sample. A mass spectrometer may use the mass (m) to charge (z) ratios of ions to separate and analyze the ions. The ion charge represents the number of electric charges of the ion The ion mass may be expressed in atomic mass units or Daltons (Da). One type of mass spectrometer is the quadrupole ion trap mass spectrometer (QITMS), which can be used to analyze the masses of atomic, molecular, and cluster ions. A QITMS typically has a ring electrode and two end-cap electrodes. In operation, a time-varying voltage is applied between the ring electrode and the end-cap electrodes to create a time-varying electromagnetic field to confine the ions within a confinement region (a trap). By varying the frequency and/or amplitude of the time-varying voltage, the ions are selectively ejected from the ion trap based on their charge-to-mass ratios. To detect the ions that are ejected from the ion trap, a laser beam is directed towards the ions, and a photodetector detects light reflected from the ions.